The Blood Coin
The Blood Coin is a red coin located in the stage Big Boo's Haunt. While most courses only contain 8 red coins, BBH contains an additional 9th red coin, the Blood Coin, located behind the shed outside the level boundary. This coin can only be accessed using GameShark codes, as Mario normally cannot go out of bounds to reach it. However, doing this is not advised, as collecting all 9 red coins can lead to problematic glitches such as polygons disappearing from Mario's model, turning in-game fog red, and erasure of save data. While it is a common misconception that collecting the Blood Coin alone directly causes these effects, they are instead caused by the red coin counter exceeding its normal range, regardless of which coin is collected last.